Great interview with Martin Müller on Chaos Radio Express 187. Discussing the history and the inner workings of Paparazzi. Enjoy!
Paparazzi features adaptive control loops that can cope with substantial “changes” of the airframe in flight. May this be a motor dropout, partial loss of control surfaces or dropping heavy payload. As videos usually say more than just words, here are two that demonstrate this.
The first video shows Paparazzi’s adaptive control loops (written by Pascal Brisset and Gautier Hattenberger at ENAC) for fixedwing aircraft keeping a Multiplex Twinstar on track, despite dropping a portion of the right wing and aileron and then switching the right motor off.
Martin Mueller equipped the Twinstar with video cameras to document this. You can easily see that after part of the right wing is dropped the adaptive controller compensates for this automatically although only 50% of the aileron control surface remains. To make things even worse, the motor on the same side was switched off to simulate engine failure but the autopilot manages to keep it stable. At that point the aircraft became virtually impossible to fly by the very skilled safety pilot in manual control.
Although the adaptive vertical control for multicopters (by Antoine Drouin at ENAC) has been around for almost two years now, here is a demo of a Paparazzi Booz quadrotor suddenly dropping 50% off its weight.
In this case, a Kalman filter of dimension one is used to estimate the the ratio of vertical acceleration over the produced thrust. This basically equates to the inverse of the mass during flight. Then the inverted dynamic model is used to issue a nominal thrust command based on this estimate. With this the quadrotor is able to stay very near same height, whereas with standard feedback control loops it would “go through the roof” when the payload is suddenly dropped.
Cheers, your Paparazzi Team
This is a brief note to keep everyone updated on progress towards supporting Paparazzi on OSX. Currently Paparazzi is supported only on Linux. With the growing base of Paparazzi developers it has become possible for us to consider supporting multiple operating systems.
Mac OSX was chosen for attention ahead of Windows 7 due to the its similarity to Linux. It is hoped that experience gained in supporting this operating system will give an indication of what form a combined build system for all three platforms will take.
The GUI used by the Paparazzi ground segment is based on GTK, this provides a transparent way of building X Windows based applications for OSX. To date all the components of the ground segment have been built in this way and function as intended. Unfortunately this currently requires hand building some packages, attention is now being given to simplifying the process by wherever possible submitting patches to the package maintainers.
Once the machinery is in place for installing Paparazzi on OSX without hand building some packages, only a few extra changes will be required to produce a version that uses the gtk-quartz-engines. This will then provide the look and feel of a native OSX application.
A number of interesting facts have surfaced during this process.
The first is that the Paparazzi development team have over the years have been very careful to adhere to the Posix standard. This has meant that very few code changes have been required to make Paparazzi to run on OSX. This portability is something the team should be very proud of.
The second is the amazing depth of talent in the Paparazzi development team. I provide only one example of this but there were many more. A central component required in the ground segment is the build system used by Paparazzi to create firmware for the autopilot. This consists of a cross compiler and related utilities. In this case Esden had already done much of the work required to produce such a toolchain with his summon-arm-toolchain script. Thanks to that with only a few “clicks” we ended up with a toolchain that we could use for both of our arm targets, lpc21 and stm32.
It is expected that instructions for installing Paparazzi on OSX with X Windows will be posted at the official Paparazzi wiki in the very near future. With a non X Windows version following in the coming weeks.
And until next time… your Paparazzi team.